Pyrosequencing Reveals the Key Microorganisms Involved in Sludge Alkaline Fermentation for Efficient Short-Chain Fatty Acids Production

Abstract

Short-chain fatty acids (SCFAs) have been regarded as the excellent carbon source of wastewater biological nutrient removal, and sludge alkaline (pH 10) fermentation has been reported to achieve highly efficient SCFAs production. In this study, the underlying mechanisms for the improved SCFAs production at pH 10 were investigated by using 454 pyrosequencing and fluorescent in situ hybridization (FISH) to analyze the microbial community structures in sludge fermentation reactors. It was found that sludge fermentation at pH 10 increased the abundances of Pseudomonas sp. and Alcaligenes sp., which were able to excrete extracellular proteases and depolymerases, and thus enhanced the hydrolysis of insoluble sludge protein and polyhydroxyalkanoates (PHA). Meanwhile, the abundance of acid-producing bacteria (such as Clostridium sp.) in the reactor of pH 10 was also higher than that of uncontrolled pH, which benefited the acidification of soluble organic substrates. Further study indicated that sludge fermentation at pH 10 significantly decreased the number of methanogenic archaea, resulting in lower SCFAs consumption and lower methane production. Therefore, anaerobic sludge fermentation under alkaline conditions increased the abundances of bacteria involved in sludge hydrolysis and acidification, and decreased the abundance of methanogenic archaea, which favored the competition of bacteria over methanogens and resulted in the efficient production of SCFAs.

Volatile fatty acids productions by mesophilic and thermophilic sludge fermentation: Biological responses to fermentation temperature

“…Table 4 shows the summary of Illumina data. The numbers of sequences and the numbers of OUTs were sufficient compared to other studies using highthroughput sequencing (Ju et al, 2014;Xia et al, 2012;Zheng et al, 2013), indicating credible representativeness to characterize the microbial communities. Shannon diversity curves also verified the adequate sample depth (Fig.…”

“…Compared with other studies which used primary or secondary sludge, or synthetic materials as substrates for fermentation (Jia et al, 2013;Wang et al, 2013;Zheng et al, 2013), the sludge used in this study had higher solids concentration, as it was reported previously that higher solids concentration could improve VFAs production (Xiong et al, 2012).…”

“…In addition, the culture-independent methods not only costs a long time, but also may underestimate the microbial diversity. Next-generation sequencing technologies can overcome these drawbacks and make it more credible to reveal the microbial community of environmental samples (Ju et al, 2014;Wang et al, 2012;Zheng et al, 2013). Among these technologies, Illumina high-throughput sequencing is a relatively cost-effective method with high coverage.…”

Characteristics of biofilms and iron corrosion scales with ground and surface waters in drinking water distribution systems

“…Then, the samples from the same pipe were mixed and lyophilized for further characterization. DNA was extracted in triplicate samples with the Fast DNA Ò SPIN Kit for soil (MP Biomedicals, Solon, OH, USA) according to the manufacturer's instructions [30]. DNA quality was checked on an agarose gel, and concentrations were measured with a NanoDrop (ND-1000, NanoDrop, USA).…”

“…DNA was amplified with bacterium-specific forward primer 341F (5 0 -Fusion A-Barcode-CA linker-CCTACGGGAGGCAGCAG-3 0 ) and reverse primer 1073R (5 0 -Fusion B-TC linker-ACGAGCTGAC-GACARCCATG-3 0 ) [30]. The PCR products of three independent reactions were pooled together, purified with the AxyPrep DNA Gel Extraction Kit (Axygen, USA), and quantified using a TBS-380 Fluorometer (Turner Biosystems, USA).…”